1, the wiring of the high-voltage part is loose, which leads to large current at startup and poor contact leading to discharge. 2. The capacitor is aging. It seems that the heating is normal. If you feel that the heating speed is slow, pay attention to the cleanliness of the microwave oven. The cavity heated by microwave oven should be absolutely clean. 3. The sound of food. Because the microwave oven heats food from the inside, if you heat food such as eggs, the food will make a noise. Solution: It is recommended to ask professional maintenance personnel to check it. If the noise comes from the microwave oven itself, it needs to be replaced with a new one or repaired before use.